Automatic telephone system



Oct. 24, 1939.

N. H. sAuNDl-:Rs

AUTOMATIC TELEPHONE SYSTEM Filed nine 19, 193e GOGAROUP 190 r-- 189 A T 132 A 3 98 A 0 2O 30 O l hl AT1" 99 I ets Sheet 1 Lama zo-GROUP 124 F16 1 "W2 12--t f GUARD TRUNK *20 INVENTOR.

NRMAN 1-1. sAuNDERs ffl/ ATTORNEY.

. Oct. 24, 1939. N. H. sAUNDERs AUTOMATIC TELEPHONE SYSTEM Filed June 19, 1936 8 Sheets-Sheet 2 INVENTOR.

NORMAN H.sAuNDERs MMM ATTORNEY.

Oct. 24, 1939. N. H. SAUNDERS 2,177,079

AUTOMATIC TELEPHONE SYSTEM l, as

fw H UNIT CONNECT INVENTOR. NORMAN H. SAUNDERS ATTORNEY.

AUTOMATIC TELEPHONE SYSTEM Filed June 19, 1936 8 Sheets-Sheefl 4 4415 483% 4 Jlu 2.o yGROUP 40 GROUP 30 GROUP 15G-GROUP GOGROUP FIG. 4

GROUP E ONNECT INE fr LI. 551g INVENTOR.

. NORMAN H.SAUNDERS ATTORNEY.

Of 24, 1939- N. H. sAUNDERs 2,177,079

AUTOMATIC TELEPHONE SYSTEM Filed June 19, 1936 8 Sheets-Sheet 5 ETD.. E VPA Alm @S mmwm m w. TI ma E E@ Y Belli w. m www 2m w E m E@ m m U v F u m E www www Nw Y.. Y E@ Y @Nw f SOI YS@ m n# EQ: m3 Y Y Y Y .v .mw am Y Y rllll Y YY Y ma El f 0 nh a@ Y ww/ Y Y mmNl Y ,Y Y Y E wlm. Y E Y Y Y mi 2 Oct. 24, 1939.

N. H. sAuNDERs ATOMATIC TELEPHONE SYSTEM 1NVENTOR. NORMAN H. SAUNDERS ATTORNEY.

Oct. 24, 1939. N. H. sAuNDERs AUTOMATIC TELEPHONE SYSTEM Filed June 19, 1936 8 Sheets-Sheet 7 E? i JP n; m no Nm zm www mmm E U.. E a. 2 .5f m n n; we EG www QFPIII. mmh mv www 5.1? L FN. mnu w3 rL. E .VII| STILI... @Qms mi S In mu, P .EN 3 ,E 2 w 2@ @2 zlft 2A. 5. L... N J| EL .MEM E .Il v Inail/.MJU E @n Ow .3S v E E: om E@ 22 w28 I .gm l :QN fm MS .L5

INVENTOR. NORMAN H. sAuNnsRs BY ATTORNEY.

Oct. 24, 1939. N. H, sAUNDERs I k2,177,079

AUTOMATIC TELEPHONE SYSTEM Filed June `19, 1936 8 Sheets-Sheet 8 INVENTOR.

` NORMAN H. SAUNDERS ATTORNEY.

Patentedv 24, 1939- PATENT OFFICE AUTOMATIC TELEPHONE SYSTEM Norman H. Saunders, Homewood, Ill., assignorl to Associated ElectricV Laboratories, Inc., Chicago, Ill., a corporation ot Delaware Application June 19, 1936, Serial No. 86,0 46

32A claims.

This invention relates in general to automatic telephone systems, but more in particular to smallv systems suited for installation in towns or villages. An'automatic telephone system of this type is generally known as a community automatic exchange or C.- A. X., and may have a capacity of about fty lines, more or less. Usually the lines are party lines having either bridged or grounded 'ringing circuits over which such subscribers are signalled by means of code ring ing. Provisions are made also for trunking calls to and from distant exchanges. 'I'he object of the present invention is vto provide a novel and improved all-relay community automatic exchange of the foregoing character and which may be considered as an improvement on the system disclosed in Patent No. 2,023,239, issued to John E. Ostline on December 3, 1935.

One of the features'of the invention relates t0 the semi-directive all-relay finder having improved testing circuits whereby the finder unit relays test two lines simultaneously in the calling group.

Another feature relates to an improved testing circuit whereby the connector unit relaysv are each used for testing one of two lines in the called group dependent upon the unit digit dialled.

Another feature relates to an improved ysubscribers line circuit having a shunt field line relay and a lockout relay.

A furtherv feature relates to an improved lock-v Referring now to the drawings, comprising" Figs. 1 to 8, inclusive, there is shown by means of the usual circuit diagrams suiiicient of the apparatus in an automatic telephone system to enable the invention to be readily understood.

Fig. 1 shows a group of finder group relays FGR for connecting the line conductors and test conductors of the various groups of lines and trunk lines to one of the nder connector allrelay links. The lines are divided into Aiive groups of ten lines Veach and are designated as the 20, 30, 40, 50, and 6D group. Relays |22, |32, |42, |52, and |62 operatively connect the test conductors of their respective groups to the link circuit shown. Relays, such as relays |20-|2|,

'line 2| by way of three-conductor cable |30-|3|, IMI-Ill, lill-lil, and INI-IBI, are for connecting the line conductors of their respective groups to the link circuit. In the lower left-hand corner of Fig. 1 is shown the line circuit LR of the first line in the 20-group. A plurality of sub-stations such as 2|I, 2|2, 2|6,

' and 2|1 are diagrammatically shown connected to this line. As will be seen, the line conductors of this line, or line 2|, terminate in contacts and ||8 in the 20-group. 'I'he line conductors and called test conductor extend by way of a three-conductor cable |59 to the outgoing end of the link wherein these conductors terminate in contacts on the connector group relays in the 20-group. In the upper left-hand corner of Fig. 1 is shown the trunk line ,circuit TLR for trunk line 20. This trunk line terminates in contacts ||0, and ||2 of the finder-group relays |2| and |22. 'I'he trunk line conductors are also connected to the outgoing end of the link in a manner similar to that described for |69. Lines 22, 23, 24, 25, 26, 21, and 28 and trunk lines 29 and 20 terminate in contacts controlled by the nder group relays of the 20-group. I'he trunk lines and subscribers lines in the 30- group and other groups are connected in a similar manner. The connect relay |10 in the lower portion of Fig. 1 operatively connects this particular link to the common apparatus of Fig. 5.

Fig. 2 shows a group of finder unit relays FUR for connecting the line of any group vto the control circuits in the link.

Fig. 3 shows a group of connector unit relays CUR for connecting the link circuit to any particular called line in any called group as determined by the operated connector group relay. The lower portion of Fig. 3 shows a unit-connecting relay 310 for connecting the connector unit relays to the link circuit.

Fig. 4 shows a group of connector group relays CGR,f or connecting the outgoing end of the link to any line in any group. In the right-hand end of Fig. 4 is shown the line circuit of line 33, and a plurality of substations thereon. Line 33 is connected to the link as shown diagrammatically by the three conductor cables|49 and 444.. All of the trunk lines and all of the subscribers lines in all of the groups terminate in the outgoing end of the link in the manner illustrated by line 33. A group-connect relay 40|) is shown in the lower portion of Fig. 4 for operatively connecting the link circuit'to the connector group relay. I'

Fig. 5 shows an all-relay allotter for preselectfof 5 are shown the link-selecting relays LSB. which control the selection of an idle link and the operation ofthe connectrelay |10 shown in thelower portion of Fig. 1. The right-hand portion of-Flg. 5 shows the'common group-start relays which control the operation of the iinder group relays shown in Fig. 1. In the lower lefthand corner of Fig. 5 is shown the allotter control relay ACR, which control diierent functions to be described hereinafter. Each group of lines has a start conductor such as start conductor 90 extending from each group of line cir-,- cuits to aterminal such as the terminal 20. The start conductor v,of the 30 group, corresponding to start conductor 90 ofsthe 20-group, would terminate in terminal 30 and the remaining start conductors lof the other groups would terminate in the correspondingly numbered terminals. Each group'of lines also has a common lock-out relay such as relay 89 in Fig. 1 and whicnis controlled over a conductor such as conductor 9| by the group-start relay.

Fig. 6 shows a group of relays in the control circuit of the link.

Fig. 7 shows another group of relays in the control circuit of the same line.

` Fig. 8 shows a further group of relays in the same link and includes the digit-counting relays.

Throughout the drawings numerous types of relays, well known in the automatic telephone art are shown'. Slow-to-operate relays are shown having a full black upper section. Slow-to-release relays are shown having a cross-hatched lower section, and vertical lines or sleeves. In Fig. 5 relay 591 has a weighted Vibrating armaf ture 598 which vibrates on deenergization of the thetest conductor of vthe calling line is marked with calling potential and the corresponding group-start vrelay is operated to energize the proper nder group control relay in an idle link previously selected by the allotter. The operation of the nder group control relays connects all. of the test conductors of all the lines in the calling group to the nder unit relays which now operate successively, each relay testing two x lines simultaneously until the marked calling line is found.

When the calling line is found the allotter is operated topreselect another idle link and the calling line is connected. to the control equipment of the link in use. The rst digit transmitted by the calling subscriber operates the counting relays to operate the corresponding connector group control relay which connects all of the test conductors of the called group to the connector unit relays of the link. The second digit reoperates the counting relays to operate the corresponding connector unit to connect the test conductor of the called line to the link control circuit. Each connector unit relay is used for connecting up two of the test conductors of two of the lines dependent upon the unit digit dialled. The third digit reoperates the counting relays to select the ringing code. If the called line is idle, a ringing relay in the link connects the selected ringing conductor to transmit the se' lected ringing code to theA calledline.

In incoming trunklcalls the operation is the same as just described with the exception that the localtalking bridges in the link are disconnected and the link is switched straight through to the trunk line. The link is then held froml the trunk line. In outgoing trunk calls the calling line is found and connected to the link in the same manner as just described and in responsive to dialling asingle digit, designating a trunk call, the corresponding connector group relay connects the test conductors of this line,

group to the connector unit relays and a portion of these latter relays then successively operate in a hunting operation tol search -for an idle trunk in this group. When an idle trunk is found the link switches straight through cutting of! the local talking bridges,

Having given a general description of the operation a detailed description will now be given. It will now be assumed that one of the subscribers on line 2| initiates a call. When the subscriber removes his receiver the circuit is completed for energizing the shunt field line relay 10 as follows: from ground through the left-hand winding of shunt-iield line relay 10, contact B3, over the calling loop to contact 62, and through the righthand winding to negative battery. It should possibly be mentioned at this time that the shunt eld line relay 10 will operate only when the line conductors of line 2 are short-circuited and will not operate in case either'one or both lines become grounded. A shunt eld relay, as is well known, has its two windings wound in opposition onto iron cores which are connected together so that it is necessary for both windings to 'be simultaneously energized before the relay operates its armature and contacts. Shunt iield line relay 10,V upon energizing, at contact 1| connects marking potential extending from negative battery through the winding of cut-oft' relay 60 to contacts 9 of iinder group relay |22. At front contact 12 relay 10 connects direct ground to test conductor 56 to busy this line and at contact 13 grounds the common start conductor 90 to cause the energization of common group-start relay 552 in Fig. 5.

Group-start relay 552, upon energizing, at' front contact 562 prepares a point in the circuit for iinder group relay 22, at contact 512 prepares a point in the circuit to the common lockout relay 89 of the 20-line group, at contact 511 completes a circuit by way of contact 543 for en-l ergizing relay 55|, at contact 518 completes its own locking circuit to grounded start conductor 90, and at contacts 519 to 582, inclusive, opens the circuits to the remaining group start relays to prevent their operation. Relay 55|, upon energizing, at contact 544 grounds conductor |92 to prepare a circuit for energizing relay |22, at contact 545 opens a point in the original energizing circuit of relay 552,"now maintained energized over its lockingv circuit, and at contacts 546 to 549, inclusive, opens further points in the circuit to the remaining group-start relays to prevent the operation of these group-start relays f in case a line in another group should initiate a call. At contact 559 relay 55| prepares a point in the locking circuit for relay 594, at contact 560 maintains' the all-link busy relay 592 in operated position, at contact 56| completes the vcircuit for operating the connect relay |10, at contact 510 prepares circuits for relays 595 and 596 and operates relay 591, and at contact 51| prepares a. 15

point in the circuit to relays 502 and 594. Relay 691 is energized from ground at amature 510 by way of contact 515 to negative battery through the winding of relay 591. Relay 591, upon operating, attracts its weighted armature 598 thereby connecting ground at amature 510 through 598 and 599 and the Winding of relay 5,96 to battery. Relay 596 energizes and at contact 569 completes the circuit for energizing slow-tooperate relay 595 from this lsame ground at contact 510. After an interval relay 595 energizes and at contact 559 shunts contact 569 and at contact 516 completes the ycircuit from grounded.

armature 510 for energizing relay 593. Slow-tooperate relay 593, upon energizing, at contact 515 opens the original circuit of relay 591. Relay 591 accordingly deenergize and releases its weighted armature 598 to cause this armature to vibrate between its two make contacts, while the contact 599 is opened. Relay 596 deenergizes when its circuit is opened at 599, but relay 595, due to its slow release characteristics, ls maintained in operated position as long as the vibrations of weighted armature 598 are oi sufficient amplitude to engage with the make contacts on either side thereof.

vThe circuit `for energizing connect relay |10 may be traced as follows: from ground by way of contacts 589, 588, 56|, 514, 501,-to start conductor |9| and thence through the winding of connect relay |10 to negative battery. At contact |l6, connectrel..y |10 disconnects conductor |85 from the guard conductor |84, at contact |12 connects the grounded conductor |92 to relay |22 to cause the latter relay to operate, at contacts A|12 to |16, inclusive, prepares circuits to the -at contact |39 prepares a point in thev test circuit for the last five lines in a group and for relay 210.

Finder group relay |22, upon energizing, at its upper contacts connects up the test leads of all the lines in the,20group, at contact |23 prepares a point in the circuit to relay |20, at contact |24 lprepares a point in the circuit to relay |2|, at

contact |25 prepares its own locking circuit to conductor |88, and at contact |28 prepares a point in the circuit to reverse battery relay 600. The circuit for energizing line relay 630 in series with relay 558 may be traced as follows: from ground through the winding of line relay 630, conductor |82, contact |29, conductor |8|, and through the Winding of relay 558 to battery. At contact 583 relay 558 prepares a point in the test circuit for relay 551 and at contact 584 completes the hunting circuit for the finder unit relays and operates relay 2|0.

Line relay 630, upon energizing, at contact 63| completes a circuit for energizing release relay 620 as follows: from ground at back contact 122, back contact 1 I1, conductor 621, normally closed contacts controlled by armature 682, conductor 626, contact 63|, and through the winding of release relay 620 to negative battery. At front contact 632 line relay 630 completesv a circuit for energizing the pulse relay 680 as follows: from ground. by way of back contact 122, conductor 629, front contact 632, and through the winding of pulse relay 680 to battery. At front contact 62| release relay 620 grounds conductor 293 and completes a circuit by way of contacts 194, 14| and 134 in multiple, through the winding of relay 120 to negative battery. Pulse relay 680, upon energizing, at contacts 68| completes a further circuit for holding release relay 626 in operated positionby way of backcontact 692, at contact 682 opens the original energizing circuit of release relay 620, and at contact 683 connects multiple ground through resistance Rl to the reset conductor 629 to maintain itself in operated position when the ground at back contact 122 is disconnected from reset conductor 629.

Relay 120 energizing, and at contact 12|, grounds conductor 626 to maintain release relay 620 in operated position. At contact 122 relay 120 opens the original circuit of relays 680 and 620 and relay 680 is now maintained in operated position through contact 683 and. the resistance RI to ground. At front contact 122 relay 120 prepares a point in the locking circuit for test relay 110A and ring-cut-oi relay 180, at contact 123 connects direct ground at the normally closed springs controlled by contact 605 to conductors 154, 295, |88, and 388, and also completes the circuit for operating relay 1|0. At contact 124 relay 12,0 disconnects one of the multiple grounds from the all-link-busy conductor 669, and at front contacts thereof grounds conductor |85 to maintain ground on the guard lead |84 when connect relay |10 deenergizes, and at contact 125 completes the circuit for operating relay 608.

The circuit for energizing relay 1|0 may be traced as follows: from grounded conductor 645 by way of 123, 135, 295, 694, 641, 111, 108, and through the winding of relay 1|0 and resistance R2 to negative battery. At contact 1|| relay 1|0 connects battery through resistance R3 in shunt of relay 6|0 by way of conductor 6|1 and contact 602, at contact 1|2 connects up dial tone, at contact 1|3 prepares a point in the circuit to relay 6|3, at 1|5 prepares a point in the circuit by means of which relay 1| 0 is later on short circuited, at contact 1|6 starts the tone machine over the tone start circuit, at 1|1 prepares points in the circuits to relay 660 and 610, at 1|8 prepares a point in the locking circuit of relay 400, and at contact 1|9 completes its own locking circuit. This locking circuit may be traced from grounded conductor 645 by way of 123, 135, 295, 694, 641, 818, 156, and 1|9. The circuit for energizing the time cut-oil relay 608 may be traced as follows: from grounded time pulse lead, through the normally closed springs controlled by contact 609 and thence by way of 654, 153, 125, 649, and through the upper winding of relay 603 to battery. At contact 605 relay-608 connects the grounded time-cutoff conductor to conductor 645 in place of direct ground, at 606 grounds conductor |85, at'601 opens' a further point in the circuit for ground all-links-busy conductor 669, and at 609 completes a locking circuit for itself from grounded time-lock conductor over its previously traced circuit.A

The finder unit relays FUR are `slightly slow to operate as well as release on account of the resistance R-included in their energizing circuit, and each finder unit relay on operating closes its X contact first. The nder unit relay 2|0 is energized in response to the operation of relay 558 as follows: from ground by way of 584, 581, |99, |19, 292, back contact 21|, 26|, re-

-sistance R, 25|, 24|, 23|, 22|, 2II, and through the winding of relay 2I8 to battery. Relay 2|8 at Xl contacts 2|2 locksitself to grounded -conductorf |88 through contacts 223, 233, 243, 253,

'and 263.' At contact 2|1 relay 2I8 prepares the test circuit for the sixth line in the calling group, at 2|6 prepares the test circuit for the iirst line in the calling group, at contacts 2 |4 and 2|5 prepares the line connections for either line 2| or line 26, at contact 2|| opens its original energizing circuit, at front contact 2|| completes the circuit for operating the second nder unit relay 220.

If the calling line is not'line 2I- or 26, then relay 228 energizes after an interval over the same circuit as traced for relay 2I8 except that in this case the circuit for relay 228 extends through front contact 2| I. At contact 222 relay 228 locks to grounded conductor |88, at 229 prepares the test circuit for line- 21 in the calling group, at 228 prepares the test circuit for line 22 in the calling group, at contacts 226 and 221 prepares the line connections for lines 22 and 21 of the called group, at contacts 224 and 225 opens the test circuit to the rst and sixth lines of the calling group,A` at 223 opens the locking circuit of the first finder unit relay 2| 8 which deenergizes after an interval, at 22| opens its original circuit, and at front contact thereof closes the circuit for the third finder unit relay 238.

The nder unit relays 238 to 258, inclusive, operate in sequence as above described until the called line is found or until relay 268 is energized in case the link fails to nd the calling line. Each nder unit relay on operating locks, opens the preceding relay circuit to cause its deenergization, disconnects the test leads closed by the preceding relay, and connects the test leads for the next two lines.

In case the link fails to nd the marked calling potential of the calling line, then relay 268 is energized by relay 258.v At 262 relay 268 locks to I grounded conductor |88, at 264 and 265 opens the test leads to the fifth and tenth lines of the calling group, at 266 opens' the circuit to finder group relay |28 to prevent its operation, at 263 opens the locking circuit of relay 258 which deenergizes, at back contact 26| opens the hunting circuit to the finder unit relays, and at front contact 26| closes the circuit for operating the 20-group lockout relay 89 as follows: from ground by Way of 584, 581, |99, |19, 292, back contact 21|, front contact 26|, conductor 288,l

512, conductor 9|, and through the 20-group lockout relay 89 to negative battery. At contact 88, relay 89 completes the circuit for operating the lockout relay 28 of trunk No. 20, at contact 8l completes the circuit for operating lockout relay 58 of line 2|, and at other similar contacts closes circuits to the lockout relays in the line circuits of the 20-group. Lockout relay 28 at contact 2| opens the circuit tothe cut-off relay 38 to prevent a call on this trunk line from marking contact |I8 with calling potential, and at contact 22 grounds the permanent alarm lead 99 to bring in an alarm. Lock-out relay 58 at contact 5| disconnects calling potential from contact |,|9, at 52 likewise grounds permanent alarm conductor 99 to bring in an alarm, and at contact 53 disconnects ground from the start lead 98 to cause the deenergization of the 20-group start relay 552 in 5, and at front contact 53 completes a. locking circuit for itself from grounded contact 13 as long as the line. relay 18 is maintained in operated position.

Group-start relay 552 deenergizes and at contact 562 opens the original circuit of relay |22 which is now held in operated position over grounded conductor |88. At 512 relay 552 opens th circuit to the common 28-group lockout relay 89 which releases, and at Y51.1 opens the circuit'to relay 55| which likewise deenergizes. At contact 88 relay 89, upon deenergizing, opens the circuit of vlockout relay 28 which deenergizes and in a similar manner at its other contacts releases the lockout relays in al1 the line circuits of group 28 in case the line relay of such circuits are not operated. At contact 8| relay 89 also opens the original circuit of lockout relay 58, but this relay is now locked in operated position due to the energized condition of line relay 18. Therefore as long as line relay 18 is maintained in operated position the lockout relay 58 is held operated Ato remove the calling battery potential from Contact ||9 at contact 5|. At contacts 545 to 549, inclusive, relay 55|, upon deenergizing, prepares the start circuits to the group-start relays, at 568 disconnects multiple ground from the all-linkbusy relay 592, at 56| opens the circuit to connect relay |18 which deenergizes, and at 518 opens the circuit to relays 593`and 595.

Connect relay |18, upon deenergizing, at 6 connects grounded conductor to guard lead |84 to operate link selecting relay 582 in series with relay 594 to cause the latter to preselect the next idle link. Aticontacts |12 to |16, inclusive, opens the circuit to` the iinder group relays, at |18 opens the point in the prepared circuit to test relay 551, at |19 opens the hunting circuit to the finder unit relays, at |29 opens the circuit to relays 558 and 638, and at |39 opens the prepared circuit to relay 218. Relay 558 deenergizes when its circuit is opened by relay |18 to open a further point in the circuit of test relay 551 at contact 583 and at contact 584 opens a further point in the hunting circuit of the nder unit relays, l

Line relay 638 deenergizes when its circuit is opened by connect relay |18,- and at contact 632 opens the circuit of pulse relay 688 and at 63| opens one of the circuits for release relay 628. Pulse relay 688, upon deenergizing, when its circuit is opened,'at 68| opens thecircuit of release relay 628, which accordingly deenergizes after an interval. Relay 628 at 62| disconnects ground from conductor 293 and releases relay 128. Shortly after. its circuit is opened slow-to-release relay 128 deenergizes and at contact 123 disconnects ground from conductors 154, 388, |88, and 295 to cause the release of relays |22, 268, and 1I8. At contact -125 relay 128 opens the circuit of relay 688 which likewise deenergizes. Relay 1|8, upon deenergizing, at contact 1|| disconnects the battery through resistance R3 from in shunt of relay 6 I 8, at 1 I2 disconnects dial tone, and at' 1|6 opens the tone-start circuit. Finder group relay |22, upon deenergizing, at its upper contact opensA the test circuit to the lines in the 28-group, and at contacts |23 and |24 opens the prepared circuit to relays |28 and I2 I. 4Relay 268 deenergizes and restores its contacts to normal. Time cut-off relay 688, upon deenergizing, at contact 685 disconnects the grounded time cut-olf lead and substitutes direct ground, at 686 disconnects ground from conductor |85 and therefore ground from the guard lead |84, and'at 681 again grounds the all-link busy conductor 669. Link selecting relay 582 is energized in series vwith the upper winding of relay 594 in response to the deenergization of relay over the following circuit; from ground at contact 608 before relay 608 deenergizes, conductor |85, contact I I8, guard lead |84, contact 5l0, upper winding of link-selecting relay 502, and through the upl per winding of relay 594 to battery. At 5|8 relay 5'02, upon energizing, closes the start circuit to the connect relay of the second link over conductor |9|' if the second link is idle, at 5|6 closes the circuit to the third link-selecting relay 503 if the second link is busy, at 5| 1 locks in series with relay 59|, and at 5|8 opens the locking circuit of relay 50|. Relay 584 energizes in series with relay 502and deenergizes when relay808 deenergizes or when relay 50| deenergizes. Relays 593 and 595 deenergize shortly after the release of relay 55|. The link has now been released, line No. v2| is locked out of service, as long as line relay 10 is in energized position, and the allotter has selected the next idle-link.

Returning now to the operation of the finder unit relays and since line 2| is the calling line,

the operation of the ilnder unit relay 2|0 therefore at contact 2 |6 completes the test circuit for operating the cut-off` relay 60 of the calling line inseries with the test relay 551 as follows: from c ground by way of contact 583 through the upper 296, 214, 266, |90, |23, and through the winding of'relay |20 to battery. At contact 586 relay 551 maintains 55| in operated position,vand at front contact 581 completes a locking circuit through its lower Winding from grounded armature 58.4. At back contact 581 relay 551 opens the hunting circuit before the next, or in this case, the second finder relay can fully operate. Test relay 551 is fairly fast to operate and therefore opens the circuit to the second finder unit relay before lt can operate to close its X" contact. Cut-ofi' relay 60, upon energizing, at 6| locks itself independent of contacts 5| and 1|, at 62 and 63 disconnects the shunt-field line relay 10, and at contact 64 operates the lockout relay 50. Lockout relay 50. at 5| opens the original circuit of cut-off lrelay 60, at 52 prepares a point in the alarm circuit, and at 53 opens the start circuit .and releases the group-start relay 552 if no other line.

line in this group is calling. Shunt-eld line relay 10 deenergizes in response to the operation of the cut-olf relay 60, and at contact 12 disconnects direct ground from conductor 56 and connects ground from the link to guard this line in the connector end of the link.

- Before proceedingv with the description, and in order to more fully describe the simultaneous testing of two lines in a group, it will'be assumed that at the time finder unit relay 2|6 is operated thatilne No. ze instead of line No. 2| is the caumg In case line 26 is the calling line, then test relay 210 is energized in series with the cut-oil' relay of the calling line over the following circuit: from grounded conductor 293, through the lowervwi'nding of test relay 210, conductor 29|,

f contact |39, conductor 284, contacts 225 and 2|1,

conductor 280, contact ||6, test conductor of calling line 26, through the normally closed contacts onthe associated lockout relay through the closed line relay contacts and through the winding of the vcut-oil? relay of line 26 to negative battery. At contact 212 relay 210 locks to grounded conductor |88, at contact 216 connects the grounded conductor 283 to the winding of the cut-off relay of line 26, at 215 opens a point in the test circuit to test relay 551, at 214 opens a point in the circuit to finder group relay |20 to prevent its operation, at 213 completes the circuit for energizing finder group relay |2| at back contact 21| opens the hunting circuit to prevent operation of the nextv nder unit relay, in this case relay 220, and at front contact 21| maintains relay 55| operated from ground by way of 584,

581, |99, |19, 292, 21|, 289, and thence over the previously traced circuit to relay 55|. Thecutofi relay of the line No. 26 operates and locks. disconnects the line relay which deenergizes, operates the lock-out relay and opens the start circuit to start-relay 552 iny a manner similar to that described for line 2|. The circuit for operating the finder group relay |2| may be traced as follows: from grounded conductor 295, contact 213, conductor |89, contact |24 and through the `winding of relay |2| to battery. At its upper contacts nder group relay |2| connects the line conductorsr of the last six lines in this group to the finder unit relays. Since relay 2|0 is operated conductors 282 and 283 are connected to the link line conductors 286 and 281 by way of contacts 2|5 and 2|4. From the foregoing description it will be seen that the finder unit relay 2|0 'simultaneously tests lines 2| and 26. In a similar manner the finder unit relays 220, 230,

240, and 250 likewise simultaneously test for two lines in the calling group.

In this case, since line No. 2| is the calling line, then nder group relay |20 is energized as previously described to connect the line conductors of the calling line to the link conductors 286 and 281 at contacts |1 and ||8. The link line relay 630 is maintained energized over the following subscribers loop as follows: from the calling loop by way of ||1 and ||8, 282 and 283, 2|5 and 2|4, 286 and 281, back contacts 182 and 193, conductors 6|1 and 6|8, contact 1|| and resistance RC to negative battery in multiple with negative battery through the winding of relay 6|0 and normally closed contact 602, and through the normally closed contacts 60| and the winding of line relay 630 to ground. The closure of contact ||1 also connects dial tone to the calling line as follows: from dial tone source by way of 88|, 81|, 148, 1|2, through the tone condenser TC to conductor 6|8,` and thence back over the previously traced circuit to contact ||1 and the calling line. At contact |26 finder group relay 20 connects ground `to the guard lead of |84 to operate relay 502 in series with relay 594 to cause the allotter to preselect the next idle link.

'I'he circuit for energizing link selecting relay 502 in series with relay 594 may be traced from grounded guard conductor |84, 5|0, upper winding of relay 582, and upper Winding of relay 594 to battery. At 590 relay 594 completes a locking circuit for itself through its lower Winding tov lead of the second link for relay 591, at |5 connects the guard lead |84' of the second link to the upper winding of link selecting relay 503 to cause the energization of this relay .if the second link is busy, at 5|1 locks itself in series with relay 59|,

and at 5|8 opens the locking circuit of link-selecting relay 50| to cause this latter relay to deenerl gize. Relay 50| energizes and at contact .501 opens a further point in the circuit to connect relay of the rst link. At 508 connects the guard lead |84' of the second link to contact 551,

at 509 disconnects the guard lead |84 of the rst link from contact 551, at 5|0 opens the` original circuit of relays 502A and 594, at 5|| opens a point in its own locking circuit, and at 5|2 closes a point in the locking circuit for relay 505. If the subsequent links are busy their guard conductors |84', |84", etc., are grounded and cause the linkselecting relays 503, 504, etc., to operate in succession until an idle linkis selected. Assuming that position from ground at contact 585, at contact 518 opens a point in its own locking circuit, and at contacts 519 to 582, inclusive, prepares the circuit to the remaining group-start relays.

Relay 591 reoperates in response to the operation of relay 594 to cause the reoperation of relay 595 and to maintain relay 595 in operated position. At the lower contact of relay 595 the locking circuit of relay 594 is opened whereupon the latter relay deenergizes. At -513 relay 594 reconnects ground to the all link busy relay 592, at front contact 514 opens the circuitto relay 591 which now vibrates its armature 598, and at back contact 514' completes the circuit Afor the connect relay of the second link over start-conductor |9|'. Armature 598 of relay 591 now vibrates causing the release of relay 595 and holds relay 595 in operated position for a certain time interval dependent upon the operated condition of relay 55|.

Connect relay |10 deenergizes in response to the operation of relay 594, and at ||6 'connects grounded conductor |85 to guard conductor |84 to maintain the link busy. At contacts |12 to |16, inclusive, relay |10 disconnects the finder group relays, at |11 disconnects grounded conductor |91 from conductor 295 and connects the grounded conductor 295 to conductor 295 to hold relay in operated position. At contact |18 relay |10 disconnects ground extending through the upper winding of test relay 551 from` conductor 294 and connects grounded conductor 293 to conductor 294 to hold the cut-o relay er1- ergized and to maintain line 2| busy. At contact |19 relay |10 opens'the hunting circuit for operating the nder unit relays, at |29 opens the circuit to relay 558, but the link line relay 530 is now held over the calling loop, and at |39 opens a point inthe circuit to relay 210. lRelay 555 deenergizes and at 584 opens the locking circuit of test relay 551. Test relay 551 deenergizes and at its contact 585 opens the circuit of relay` Relay 55| deenergizes, and at contacts 555 to 549, inclusive, prepares the start circuit for the group-start relays. At 550 relay 55| removes circuit, and at 515 opens a the multiple ground from the all-link-busy relay 592, at 56| opens the circuit to the connect relay, at 510 opens the circuit to relays 593 and 595, and at 51| opens the circuit to relay 594. Relay 593 deenergizes alter an interval andat 515 pre-J5 pares the circuit for relay 591. deenergizing, Yat 559 opens a point infits own point inthe circuit to relay 593. '5

The foregoing operations'have all taken place in response to the initiation of a call and when the calling subscriber hears dial tone such subscriber then dials the digits necessary to connect with and ring the desired called line. Line relay 530 follows the pulses transmitted andv -deenergizes for each pulse. Line relay 530 deenergizes on the rst pulse and at 63| opens a multiple circuit to release relay 520, whichfhowever, is maintained in operated position during the pulsing period. At front contact 532 relay 530 'opens the circuit to pulse relay 580, which deenergizes and at back contact 532 closes the priming circuit to assist in reenergizing link line relay 530 over the subscribers loop. This priming circuit may be traced` through the resistance R4, contact 522 and back contact 532, through the winding of relay 680. The resistance R4 is of sucient resistance to prevent the operation of relays 530 and 580 but primes line relay 530 so that it responds to the impulses over the subscribers loop.

Pulse relay 580 deenergizes and at 58| temporarily opens the circuit to slow-to-release relay 520, and at 582 disconnects ground from the hold lead and grounds the pulse lead.

On eachodd pulse ground on the pulse lead closes the circuit to relays 5.40, 550, and 510.- On each even pulse ground on the pulselead closes 550, 550, and 510. The circuit for energizing relays 540, 650, and 510 may be traced as follows: from grounded contact 12|, conductor 525, normally closed contacts controlled by contacts 552, pulse lead 621, :front contact-1|1, conductor 528, back contact 5|5, and in multiple through the windings of series hold relay 510, the upper winding of hold relay 550, and by way of contact 55| through the upper winding of relay 540. At contact 55| hold relay 650 prepares a point in the hold circuit for relay 640 and a point in the energizing circuit of relay 550, at 552 also prepares a holding circuit for relay 540 and for relay 550, at front contact 563 completes the circuit for operating the group-connect relay 400, at 555 prepares a new holding circuit for relay 1|0, and at` 565 grounds contacts 544. vSeries hold relay 510, upon energizing, at 51| completes a holding circuit through the lower winding of hold relay 550, and at 612 prepares a new circuit for relayA 580. Ocld relay 540, upon energizing, at contact 54| prepares a hold circuit through its lower winding as well'as the energizing circuit for the lower winding of relay 550,r at 542`con nects the hold conductor through the lower windings of relays 540 and 550, at 543 prepares a new circuit for the relay 580 and relays 540 and 550, and at 644 ground the odd conductor to energize the rst counting relay 8|0.

At the end of the first pulse line relay 630 is reenergized over the subscribers loop and is assisted in its operation due to the previously mentioned priming circuit including the resistance R4. At contact 53| relay 530 recloses the circuit to slow-to-release relay 620 before .it has `had sumcient time to release, at back contact 532 opens the priming circuitl and at front vcontact Relay 595, upon 532 closes the circuit for pulse relay 580, relay 656, and completes the circuit for holding relay 646. The circuit for pulse relay 686 may be traced as follows: from ground by way of 643, 653, 612, 632, relay 686 to battery. Pulse relay 686 reenergizes, and at 68|, recloses the circuit to release relay 626, at 682 grounds the hold con ductor to hold relays 646 and 656, and disconnects ground from the ypulse ,lead 621 to open the original energizing circuit of relays 646, 616, and 686. Relay 616, due to its slow-release characteristics, is maintained energized during the impulsing period. At 683 pulsing relay 686 again completes its own locking circuit through resistance Rl. The circuit for operating reset relay 656 is as follows: from grounded contact 643, 653, 612, 632, 662, 652, 64|, and' through the lower winding of relay 656 to negative battery. Relays 646 and 656 are likewise held in operated position by way 'of contacts 64|, 642, and 66| to the hold conductor which is new grounded over 682, 626, and 12|. Relay 656, upon energizing, at back contact 65| opens the 'original energizing circuit of relay 646 which is now held through its lower winding, at front contact 65| prepares a holding circuit for its upper winding, at 652 opens a point in the original circuit and thev holding circuit of relay 646, and at 653 opens the energizing circuit of relay 686, but the latter relay is now held operated through its own contacts 683. y

At the start of the second pulse line relay 636 is deenergized over the loop circuit. At 632 line relay 636 opens the locking circuit of pulse relay 686 and re-establishes the priming circuit. Pulse relay 686 deenergizes, and at 682 disconnects ground from the hold lead, thereby opening the holding circuit of relay 646 and also grounds the pulse lead to maintain the series hold relay 616 and 666, as well as 656 energized. Odd relay 646 deenergizes after an interval and at contacts 64| and 642 opens the circuit through the lower winding of relay 656 which is now held in operated position over its upper winding. At`

643 .relay 646 prepares a new circuit for reenergizing pulse relay 686, and at 644 disconnects ground from the oddr conductor and grounds the even conductor to operate counting relay 826.

At the end of the second pulse llne relay 636 is reenergized over the subscribers loop to again completevthe circuit to-hold release relay 626 in energized position at contact 63|, and at 632 completes the circuit for reenergizing the pulse relay 686. 'I'his circuit may be traced as follows:

from ground, back contact 643, front contact 653, 612, 632, and through `thejwindirlg of vpulse relay 686 to battery. At 682 relay 686 Iagain grounds the hold lead without effect at this time since the relay 646 is in deenergized positionand at the normally closed contacts controlled by contact 682 disconnects ground from the pulse lead to restore relay 556. Relay 656 at 65| reestablishes the original circuit of relay 646, at 852 prepares `a point in the holding circuit for relays 646 and 656; and at 653 prepares the circuit for pulse relay 686. y

At the start of the third lpulse line relay 636 again deenergizes and opens pulse relay 686 which releases. At 682 pulse relay 686 reestablishes the circuit for relays 646, 666, and 616. Relay 646 reenergizes to prepare the circuits for relays 656 and 686, and at contact 644 grounds the odd conductor to operate the third counting relay 836. At the end of the third pulse line relay 636 and pulse relay 686 are reoperated and relay 656 is reenergized. At the start of the fourth pulse line relay 636 and pulse relay 686 deenergize and cause the deenerglzation of relay 646. Relay 646 at contact 644 grounds the even conductor to operate the fourth counting. relay 846.

` In the` same manner as just described relays 646 and 656 are energized on each odd pulse and deenergized for each even pulse for the remaining pulses. At contact 644 each energization of odd relay 646 grounds the odd lead to cause the energization of the succeeding odd counting relay and on each deenergizaton of odd relay 646 contact 644 grounds the even lead to energize the succeeding even counting relay.

The counting relays are shown in Fig. 8 and comprise relays 8|6 to 866, inclusive. These counting relays are adjusted so that their locking contacts marked with an X are first. to operate to close-the locking circuit of such relays. When the odd conductor is grounded in response to the rst odd pulse counting relay 8|6 is energized by Way of contacts 853, 845, 835, and 823. At 8|| relay 8|6 prepares the circuit over the No. l conductor of cable 369, at 6|3 opens the locking circuit of connect relay 466 if only one pulse is transmitted, at 8|4 connects the even conductor to the second counting relay 826, at 8|5 4locks itself by'way of contacts 825 and conductor 896 which was grounded in response to the op'- as will be subsequently described, and at 8|8 connects the No. 1 ring conductor to contact 895.

In response to the even pulse, the even conductor is grounded to energize the second counting relay 826 by way. of contacts 854 and 8|4. At 82| relay 826 prepares aconnection to the No. 2 conductor of cable 369, at 823 connects the third counting relay 836 to .the odd conductor, at 824 locks itself to grounded conductor 396 by way of contacts 838, 841, and 856, at 825 opens the locking circuit of the first counting relay 8| 6 which accordingly deenergizes and at 821 connects the No. 2 ring conductor to contact 896. In response to the third pulse the odd pulse conductor is again groundedand this time completes the circuit for energizing the third countingI relay 836 by way-of contacts 853, 845, and

eration of the group-connect relay 466 in Fig. 4,

823. At 83| relay 836 prepares the circuit for the No. 3 conductor of cable 369, at 835 opens its original energizing circuit after completing its `locking circuitat contact 831, at 836 prepares the v by way of contacts 854 and 636. At 84| relay 846 prepares the circuit over the No. 4 conductor of cable 369, at 845 prepares the circuit for the fifth counting relay 856, at 846 locks to grounded conductor 396 by way of contact 856, at 841 opens the locking circuit of the third counting relay 836 which deenergizes, and at 849 connects the No. 4 ring conductor to contact 896.

In response to the fifth impulse the odd pulse conductor is grounded the' third time to complete the circuit for the fifth counting relay 856 by Way of contacts 853 and 854. At relay 856 prepares the circuit over the No. 5 conductor of cable 368, at 853 opens its original energizing circuit after completing its locking circuit at sixth counting relay 868, at 855 locks itself by way of contact8|6 to grounded conductor 398, at 856 opens the locking circuit of counting relay 848 which deenergizes, and -at 858 connects the No. 5 ring conductor to contact 895. e

In response to the sixth pulse transmitted from the calling line the even pulse conductor is grounded a third time to complete the operation of the sixth counting relay 868 byl way of front contact 854. At contact 86| relay 868 prepares the circuit for the No. 6 conductor of cable 369 by way of contact 852, at 862` prepares a point in the circuit to relay 888, at 863 prepares a point in the circuit to relay 6|3, at 864 shunts contacts 8|3, at 865 prepares a new circuit for reenergizing the first counting relay 8I8, at contacts 866, 861, and 868 prepares the circuit for reversing the application of ringing current to the called line, and at 869 locks itself to grounded conductor 398.

In response to the seventh pulse the odd pulsev conductor is grounded a fourth time to cause the reoperation of the first counting relay 8I8 by way of 865, 845, 835, and 823. At 8I2 relay 8I8 prepares a point in the circuit to the No. 7 conductor of cable 369, at 8| 4 prepares the circuit to the second counting relay 828, at 8|5 locks itself, at 8|6 opens the locking circuit of the fth counting relay 858 which accordingly deenergizes, and at 8I1 connects the No. 2 ring conductor to contact 893.

In response to the eighth pulse the even pulse conductor is grounded a. fourth time to energize relay 828 by way of contacts 854 and 8|4. At 822 relay 828 prepares the connection for the No. -'conductor of cable369, at 823 prepares the circuit for the third counting relay 838, at 824 locks itself, at 825 releases the first counting relay 8I8, and at 826 connects the No. 3 ring conductor to contacts 894.

In response to the ninth pulse the odd pulse conductor is grounded a fifth time to reenergize the third counting relay 838 over the previously traced circuit. At 832 relay 838 connects the No. 9 conductor of cable 369, at 833 prepares a point in the circuit for relay 348 if this is the first digit transmitted by the calling subscriber,

at 834 prepares a point in the circuit for relay 6|3 if this is the first digit transmitted by the callingsubscriber, at 835 opens its original circuit after locking at contact 831, at 836 prepares a circuit for the fourth counting relay 848, and at 839 connects the No. 4 ring conductor to contact 893. K

In response to the tenth pulse the even pulse conductor is grounded the fifth time to energize the fourth counting relay 848. At 842 relay 848 prepares the circuit over the No. 10 conductor Vin cable 369, at 843 prepares a point in the circuit to relay 348 if the digit just dialled is a first digit, at 844 operates relay 6 I3 in case this digit is a first digit, at 845 prepares the circuit for the fifth countingrelay 858, at 846 locks itself, at 841 releases the third counting relay 838, and at'848 connects the No. 5 ring conductor to contact'894.

Group-connect relay 488 is energized in response to the energization of relay 668 over the following circuit. Fromground by way of front contact 663, back contact 186, 149, 815, 883, 455, and through the winding of group-connect relay 488 to battery. At 4|9 connect-relay 488 connects grounded conductor' 293 to conductor 456, at 429 prepares a point in the circuit to connector unit re1ay'358, at 439 prepares the locking circuit for the counting relays byggrounding conductor 398, at 449 completes the locking circuit for itself, at 459 prepares a point in the circuit to transfer relay 888, at contacts 498 to 498, inclusive, connects the connector group relays to the counting relay contacts, and at 469 prepares a point in the circuit to relay 6|3 in case the rst digit dialled is either 9 or 0. A

After each' digit dialled by the calling subscriber line relay 638 and pulse relay 688 are held in energized position for a sufiicient length of time to cause the deenergization of slow-to-release series hold relay 618, since the energization of pulse relay 688 disconnected ground from the pulse conductor. Series-hold relay 618 therefore deenergizes shortly after each impulsing periodand at 61| opens the holding circuit of series-hold relay 668,` which likewise deenergizes. At 66| and 662 relay 668 causes, the release of relays 648 and 668 if the same should be energized, at front contact 663 opens the original energizing circuit of relay 488 which is now maintained in ,operated position over its locking circuit, at back contact 663 grounds the contact 86| to operate the connector group relay prepared dependent upon the last counting relay energized,

Iand at 666 disconnects ground from the even and odd conductors to prevent further impulsing to the counting relays. The locking circuit for the group-connect relay 488 may be traced as follows; from grounded conductor 645 by way of contacts 123, 1|8, 155, 885, 8|3 (or 864), conductor 454, contact 449, and through the winding of relay 488 to battery.

In case the i'lrst digit dialled by the calling subscriber is 1, which in this case is considered a.preliminary impulse, counting relay 8I8 is energized and at contact 8|3 opens the locking circuit of group connect relay 488 so that this relay will deenergize when relay 668 deenergizes in order to cause the release of the operated counting relay. In case the first digit dialled is 2, 3, 4, 5, or 6, then counting relay 828, 838, 848, 858, or 868 is operated, and when relay 668 deenergizes to ground contact 86| a circuit is completed for operating the corresponding connector group relay or relays 428, 438, 448, 458, or 468. In case the first digit dialled is 9, then relays 438 and 6|3 are operated when relay 668 deenergizes. If the rst digit is 0, then relays 428 and 6|3 are operated in response to the deenergization of relay 668 as will be more fully described in connection with trunk calls.

Assuming now that line No. 33 is being called by the calling subscriber, then the first and second digits are 3 and 3, respectively, after whch the ringing digit is dialled. In this case counting relay 838 is operated and when relay 668 deenergizes after the impulsing period for the first digit connector-group relay 438 is energized over the following circuit: from -ground by Way of back contact 663, conductor 634, 115, 446, 86|, 83|, conductor 3 of cable 369, 493, and'through the winding of connector group relay 438 to negative battery.` At its upper contacts connector group relay 438 connects the test leads of all the lines in the 30-group to the test conductors extending to the connector unit relays, at 433 prepares the circuit for connector group relay 432, at 434 prepares a circuit for connector group relay 43|, at 435 completes its own locking circuit to grounded conductor |88, andat 436 completes the circuit for operating relay 888. This circuit may be traced as follows: from ground by way of 621|, 293, back contact 11|, 458, 436, 459, 392, 3| I,

321|, 33|, 34|, 35|, conductor |2 of cable 369, back 75 contact 862, and through the winding of transfer relay 880 to battery. At contact 88| transfer relay 880 disconnects dial tone from the calling line, atl 882 completes its own locking circuit from grounded conductor 458, at back vcontact 883 .opens the original energizing circuit of relay 480, atfront contact 883 prepares a point in the circuit tol connect relay 310, and at 885 opens the locking circuit of groupvconnect relay 400, which deenergizes. At contact 429 relay 400 opens a point in the circuit to relay 360, at 439 disconnects ground from conductor 390 to open the locking circuit of the operated counting relay, in this case relay 836, at 459 opens the original circuit of transfer relay 880 now locked in operated position, at contacts 492 to 499, inclusive, opens the circuit to the connector group relays, and at 469 opens a point in the circuit to relay 6|3.

'I'he calling subscriber may now dial the second digit, or digit 3. Relays 638, 686, 648, 650, 660, and 610 are operated as previously described to cause the operation of counting relay 830. At front contact 663 relay 660, upon energizing in response to the second digit, completes the .circuit for energizing connect relay 310 as follows: from ground, front contact 663, 633, 10'6, 149, 815, front contact 883, 381, and through the winding of unitconnect relay 31|) to battery. Relay 3l6energises, and at 383 locks itself by way of 388, 814, 154, 145, and 123 to grounded conductor 645. At contacts 31| to 315, inclusive, prepares circuits for the connector unit relays 3|0 to 350, inclusive, and at contacts 316 to 380, inclusive, prepares other circuits for these same connector unit relays. At contact 38| relay 310 prepares a point in the circuit to relay 360. at 384 prepares a circuit to relay 810, and at 385 grounds conductor 398 to provide a locking circuit for the operated counting relays.

. After the second digit 3 hasv been transmitted by the calling subscriber relays 610 and 660 deenergize as before, and relay 660 at front contact 663 opens the original energizing circuit of connect relay 310, and at back contact 663 completes the circuit for energizing connector unit relay 330 as follows: ground, back contact 663, conductor 634, 115, 446, 86|, 873|, conductor 3 of 369, 313, and through the winding of connector unit relay 330 to battery. At contact 338 relay 330 prepares a point in the test circuit for line No. 38 only when connector unit relay 330 is energized at the-same time as relay 360. At 331 relay 330 connects the test lead 443 of line 33 to test relay 110. At contacts 335 and 336 connects the line conductors 366 and 365 of the link to con-y ductors 395 and 396, at 334 completes the circuit for energizing relay 810, at 333 opens the locking lcircuit to relay 320 if operated, at 332 locks lil itself to grounded conductor |88, at; back contact 33| opens the original energizing circuit of relay 886, and at front contact prepares a point in the trunk-hunting circuit which is used only in case three trunks are included in one group.

The circuit for energizing relay 810 may be traced as follows: from ground by way of contact 334, by way of 384, 389, and through the J 310 which deenergizes, at 815 opens a further point in the original circuit of relay 310, at 816 prepares a point in the locking circuit for the counting relays, at 811 prepares a point in the circuit to relay 180, at 819 prepares a point in the circuit to ring relay 388, and at 818 opens the locking circuit of relay 1|6, but this latter relay is held operated by way of 108, 111, 694, 135, and 123, to grounded conductor 645. Unit connect relay 310 deenergizes when its locking circuit the connector unit relays for a line in the last five of a group is` slightlydifferent. In order to describe this operation it will be assumed for the time being, that the second digit dialled is 8 instead .of three. In this case it will be remembered that counting relays 820 and 860 are operated in response to dialling digit 8. Now, when relay 660 deenergizes after the second digit connector unit relays 330 and 368 are operated.

The circuit for operating relay 360 may be traced as follows: from ground by way of back contact 663, 634, 115, 446, front contact 86|, conductor of cable 369, contact 38|, and through the winding of relay 360 to battery. Relay 360, upon energizing, at back contact 363 disconnects the link test lead 364 from the test contacts of the first five lines in the group, and at front contact 3'63 connects the link test conductor 364 to the test contacts of the last ve, l,ines in the called group. At back contact 362 relay 360 opens the circuit prepared for connector group-relay 432, at front contact 362Y prepares a point in the circuit for connector group relay 43|, and at 36| locks to grounded conductor |88. The circuit for energizing connector unit relay 330 is the same as that previously described up to contact 86| and thence through its front contact by way of contact 822 since counting relay 820 is operated with counting relay 860, over conductor 8 of cable 369, contact 318, and through the winding of connector unit relay 330 to battery. At contact 332 relay 330 locks to grounded conductor |88. by way of back contact 343 and 353, at 338 connects the link test conductor 364 to the test lead of line 38. At 335 and 336 prepares the line connections, and at .334 operates relay 810 as before. Relay 810, upon energizing, causes the release of unit connect relay 310, and the deenergization of the operated counting relays 820 and 860. Unit connect relay 310 deenergizes and releases the counting relays 820 and 860 by disconnecting ground from conductor 390. The operation from this point on is the same for line 38 as for line 33.

Assuming now that line No. 33 has been connected with, the calling subscriber may now dial the ringing digit to selectively ring the desired subscriber on this line. In case ringing digit is dialled, then ringing current will extend from the ring lead No. 1 from the ringing interrupter (not shown) over the positive line to signal subscriber No. 331. Relays 638, 686, 649, 65|), 660, and 610 are operated in response to the ringing digit, as previously described. In this case, since digit is dialled, then counting relay 8|0 is operated as before. Relay 660, upon energizing for the third digit or ringing digit, at back contact 663, opens the locking circuit of relay 880 which deenergizes.

At 664 relay 660 completes the circuit for operating relay as follows: from grounded conductor |88 by way of 811, 639, 848, 638, and through the winding of busy relay 100 to battery. At 665 relay 660 completesa new holding circuit for relay 1|0 as follows: from grounded conductor 645 by way of 123, 135, 295, 694, 665, 646, and through the winding of relay 1I0 and the resistance R2 to negative battery. Relay 880 deenergizes in response to the operation of relay 660 and at 884 connects grounded contact 816 to conductor 390 to provide a locking circuit for the counting relays. ing, at 10| shunts the winding if relay 6 0 by connecting battery through resistance R3 thereto, and at 102 prepares a point in the busy tone circuit, at 103 prepares a point in the circuit for grounding conductor 364 incase the call is a revertive call, and at 104 prepares a point in the circuit for revertive relay 130, at 105 connects multiple ground to the tone-start lead, at 106 completes the circuit for operating relay 126 by way of conductor 633 and iront contact 663, at 101 completes its locking circuit by way of back contact 116 and grounded conductor |88, at 108 opens one of the circuit holding relays 1|0 in energized position, and at 109 opens a point inthe circuit to ring relay 890. Relay 126 energizes and at 121 prepares a point in the test circuit for test relay 110. Counting relay 8| 0 is energized in response to the ringing digit l,'and at 8|8 prepares the ringing connection.

After the last pulse of the ringing digit relays 660 and 610 release as previously described. At front contact relay 660 opens the circuit to the slow-to-release relay 126, and at back contact 663 completes the test circuit for test relay 110 and cut-off relay 41| in case the called line is idle, and at 665 opens the holding circuit of relay 1|0 which accordingly deenergzes.

If line 33 is busy, then the test lead 443 of the called line'will be grounded to short circuit test relay 110 to prevent its operation over the following circuit: from ground by Way of back contact 663, conductor 634, contact 121 of the slow-torelease relay 126, through the lower winding of test relay 110, link test conductor 364, back contact 363, conductor 349, contact 331, conductor 391, contact 4| 3, test conductor 443, to busy ground at the called busy line. After an interval, slow-to-release relay 126 deenergzes and at 121 opens the test circuit through the lower winding of test relay 110 to prevent the seizure of line 33 in case it should become idle. Relay 1I0 deenergzes in response to the release of relay 660, and at 1|2completes the busy tone circuit which may be traced as follows: from busy tone source, by way of 102, 1|2, tone condenser TC, back contact 193, conductor 281, contact 214, conductor 283, contact H1, to the calling line loop. At back contact 1| 3 relay 1|0 prepares a point in the circuit to relay 6I3, at 1|4 prepares a point in the circuit for grounding test conductor 364 on a reverting call, at 1|6 removes one of the multiple ground connections from the tone start lead, at 1|1 connects the pulse lead to the reset lead to prepare a circuit for reoperating relay 680 if the circuit to line relay 630 is again interrupted for a reverting call, and at 1 I8 disconnects ground from conductor 155. When the subscriber hears the well known busy tone such subscriber will replace his receiver and release the apparatus in a manner more fully described hereinafter.

If line 33 is idle then test relay 110 is not short circuited and is operated in series with the cut-off relay 41| of the called line as follows;

Busy relay 100, upon energizfrom ground by way of back contact 663, conductor 634, contact 121, through the lower winding -of test relay 110, st conductor 364, back contact 363, conductor 349, contact 331, conductor 391, contact 4l3, conductor 443, back contact 483, ,.5 and through the winding of cut-oil relay 41| to battery. At 11| test relay 110 completes a locking circuit through its upper winding of grounded conductor 293, at 1 12 connects direct ground from front contact 122 over the link and called line test conductor to hold the cut-off relay and the called line busy, at 113 connects-ground to the generator start lead to start the ringing machine, at v115 disconnects ground irom conductor 446, at back contact 116 opens the locking circuit of busy relay 100 which deenergizes, at front contact 116 completes the circuit for operating the connected group relay 432 or 43|, dependent upon the operated condition of relay 360, at 111'opens a point in the circuit of relay 1|0 to prevent its reenergization in response to the release of relay-100. and at 118 prepares a point in the circuit to ring relay 890. Relay 100, upon deenergizing, at 10| disconnects the battery shunt from around the winding of relay 6|0 to allow this relay to operate over the calling subscribers loop, at 102 disconnts the busy tone from the calling line, at 105 disconnects ground from the tone start lead to stop the tone machine, and at 109 connects the pick-up lead to ring relay 890.

Cut-olf relay 41| of the called line, upon energizing, at 411 connects the grounded test conductor 443 to test conductor 484 to busy this line in the nder end of the link, at 418 and 419 disconnects the shunt-field line relay 412, and at 480 operates lockout relay' 410. In this case, since nder unit relay 360 is not operated, then the connector group relay 432 is operated in response to the operation of test relay 110 over the following circuit: from grounded conductor 645, by way of 123, front contact 116, conductor 368, back contact 362, conductor 394, contact 433, and through the winding of connector group relay 432 to battery. At contacts 4|4 and 4|5 relay 432 connects the line conductors of the link to the line conductors 4 85 and 486 of the called line.

At the beginning of each ringing cycle the ringing machine grounds the pick-up lead 659 momentarily and nowl operates ring relay 890 as follows: from grounded pick-up lead by way of contact 819, conductor 661, 109, 146, 118, 151, 899, and through the winding of ring relay 890 to battery. Ring relay 890 energizes, and at its X contact 898 completes its own locking circuit before open- A ing contact 899. At contacts 89| and 895 relay 55 890 connects the No. I ring conductor to the positive line 486 of the called line,at 892 connects the negative line of the called line to the ring-cut-off relay 180, at 891 completes the ringback tone circuit to the calling line, and at its remaining contacts prepares the ringing circuit for connection to the remaining ringing leads in case other ringing digits are dialled. Interrupted grounded generator connected to ringA conductor No. l now extends by way of 8|8, 895, 868, 866, 89|, 131, 182, 366, 335, 395, 4|5, 486, and through the switchhook and ringer of the rst five subscribers lines in this group to ground. The proper ringing code is transmitted over this circuit to signal the called subscriber at 33|. The ring back circuit to the calling subscriber may be traced from ring conductor No. l by way of 891, 138, ring-back condenser RBC, 193, through the operated contacts on the finder unit and ilnder group relays to the calling line conductor.

In case the ringing digit is six `or more, then counting relay 860 is energized and the ring lleads I to 5 are connected, dependent upon the other counting relays energized, to the negative line conductor of the called line by way oifront contact 861, while the vpositive line conductor of the called line is connectedto the ring-cut-oil' relay 180 by way of front contact 866 and conductor 138. The remaining subscribers on the called line, having their ringers connected to the negative line conductor,l are selectively signalled in a manner apparent from the foregoing description.

When the called subscriber answers the ringcut-oif'relay 160 is energized over the called line loop over the previously traced ringing circuit and thence back over negative line conductor 485,

contact 4 I4,- conductor 386, contact 336, conductor 365, contact 18|, 'conductor 136, contact 882, back contact 861, conductor 139, and through the upper winding of ring-cut-oi relay 180 to negative battery. Ring-cut-off relay v180 energizes over` the above traced circuit, and at X contacts 183 completes its locking circuit to grounded contact 122. At contacts 18| and 182`ring-cut-oi! relay opens the ringing circuit and completes the circuit for operating relays 150 and 6|3 over the called line loop.

Relay .150, upon energizing in series with relay 6 |3 over the. called loop, at 15| completes the circuit for operating slow-to-operate relay by way of 116 and grounded conductor |88. At 162 relay prepares a point in the circuit for the reverse relay 600, Vand-at 153 opens the locking circuit of relay- 608 which releases. Relay 6|3 is energized overthe called loop and performs no useful function at this time except to feed talking battery along with relay 150 to the called line. Cut-oi relay 608, upon deenergizing, at contact 605 disconnects the time-cut-off ground and substitutes direct ground to the link to'prevent disconnection of this link when the time-cut-oil ground is removed. -This time cut-ol ground is effective to release the link in case the link has not reached talking condition within a predetermined time. Relay 140, upon energizing, at 14| removes the shunt from around contact 134, at 142 completes its own locking circuit, at 143 disconnects ground from the generator start lead to stop the ringing machine, at 144 completes the circuit for operating the reverse relay 600, at 145 disconnects ground from conductor 15'4 to release relays 810 and 880, and at 146 opens a point in the original circuit of ring relay 890. The circuit for operating the reverse relay 600 may be traced as follows: from grounded conductor 645 by Way of 123, 135, 295, 684, 641, 152, 144, 635, 6||, |86, |28, |81, and through the winding of relay 600 to battery. It should possibly be mentioned at this time that contacts such as contacts |28, |38, |48, |58, and |68 are -provided for each group of lines in case such lines require reverse battery supervision for operating a meter or other purposes. At contact 603 relay 600 completes its own locking circuit to 635, and at contacts 60| and 602 reverses battery back over the calling line loop to operate a meter for coin collect or to give supervision if required. Ringing relay 890 deenergizes in response to the operation of relay 140 and opens the ringing and ring-back connections to the ringing machine. Relay 810 deenergizes in response to the operation of relay 140, and 'at contact 816 disconnects ground from conductorA 380 v to unlock the operated counting relay to cause the release of the same. The connection between the calling line 2| and line 33 is now completed over the heavy talking vconductors including conductors 286 and 281, back contacts 16| and 162, front contacts 18| and 182, andv conductors 365 and 366.

Release When the called subscriber replaces his receiver the called line loop is opened and relays 150 and 6|3 deenergize. At 15| relay 150 opens the original circuit of relay 140 now locked energized, at 152 opens the circuit to relay 600 which releases and reverses battery, and at 153 reoperates relay 608. Relay 608 energizes and locks as previously described, and at 605 disconnects vground and substitutes the time-cut-ol ground so as to automatically release the link after a predetermined' time if the calling subscriberfails to hang up.

When the calling subscriber replaces his receiver relays 6|0 and 630 deenergize. At 63| relay 680 disconnects one multiple ground from release relay 620, and at 632 releases relay 6.80. At 68| relay 680, upo'n deenergizlng, opens the circuit of slow-to-release relay 620 which deenergizes after an interval. At 62| relay 620 disconnects ground from conductor 293, opens the circuit to relays 120 and 110, removes the busylng ground from the calling line, and causes the release of cut-off relay 660. Test relay 110 deenergizes when its locking circuit is opened by relay 620, and at 112 disconnects ground from conductor 364 and test lead 443 of the called line, thereby opening the circuit of the cut-oft' relay 41| to free the called line. At contact 116 relay 110 opens the locking circuit of relay 140 which releases and also opens the circuit to the operated connector group relay 43| or 432 which thereupon deenergizes. Slow-to-release relay 120, upon deenergizing, at 122 opens the locking circuit of ring-cut-oi relay which releases, and at 123 disconnects grounded conductor 645 from conductor 295 to release iinder group relay |20, disconnects ground from conductor |88 to release the operated connector group relay 430, the operated connector unit relay 330 (relay 360 if operated), the operated nder unit relay 2|0 (210 if also operated), and finder group relay |22. At'front contact 124 relay 120 removes one of the multiple ground connections from the guard leadY ductor 558 to maintain the all-link-busy relay- 592 energized. Finder group relay |20, upon deenergizing, at contact |26 disconnects ground from the guard lead |84 to make this link available for use on other calls. Relays |20, |22, 2|0, (210 and 3601i` operated), 330, 430, and 432 deenergize and disconnect the calling and called lines from the link. Relay 140 and the remaining link relays now restore to their normalposition. The cut-olii relays 60 and 41| of the calling and called lines deenergize when their circuits are opened to open the circuits to their associated lockout relays 60 and 410, which likewise deenergize after an interval providing the associated line relays 10 and 452 do not operate when the cut-oil relays release. All of the apparatus is now restored tonormal position and may be used on subsequent calls.

Reverting calls subscriber on his own line or subscriber 2| In response'to the initiation of a call an idle link is connected torline 2| by the operation of the finder relays |20, |22, and 2|0 as previously described. In response to dialing digits 2 and 1, the

' to cause the release of relays 6|0 and 630. Line relay 63.0, upon deenergizing, at 632,'opens the circuit of relay 680 which likewise deenergizes. Relay 680, upon deenergizing, at front contact 68| lopens the circuit of slow-to-release relay 620 and at back contact 68| completes a holding circuit for holding the cut-oil relay 60 of the calling line because relay 100 is still in energized position and because the test relay 110 did not operate. Ground is connected to the test lead 56 of the calling line because in this case the calling and called lines are the same. 'I'he circuit for holding the cut-ofi:` relay 60 in energized position may be traced as follows: from ground by way of back contact 68|, back contact 69|, 623, 103, 1|4, 364, back contact 363, conductor 349, contact 3.|1, upper test contact of connector group relay 420 for line 2|, conductor 56 of cable |59 to the calling and called line circuit, back contact 12I and through the winding of cut-off relay 60 to battery. This same ground also maintains relay 120 in operated position and operates reverting relay 630 as follows: from ground over the previously traced circuit to the cut-off relay 60 and thence by Way of contact 6|, contact H9, conductor 28|, contact 2|6, contact 224, conductor 285, 215, 294, |18, 293, contact 194, contacts 134 and 14| in multiple and through the winding of relay 120 to battery.

Relay 120 isl maintained energized over this circuit and when release relay 620 deenergizes this same ground continues by way of back contact 62|, conductor 625, contact 104 and through the winding of reverting call relay 130 to operate relay 130. At contact 13| reverting call relay 130, upon operating, connects direct groundto link test conductor 364 to hold the cut-oi relay 60, and slow-to-release relay 120 operated, at 132 completes a locking circuit for itself independent of contact 104, and at 133 connects grounded conductor 293` through the upper winding of test relay 110 to cause this latter relay to operate, at 134 opens the shunt around contact 14|, and at 135 disconnects ground from conductor 295 to release nder group relay |20.

Finder group relay |20 accordingly deenergizes and at contacts ||1 and ||8 disconnects the line from the nder end of the link, and at |26 removes one of the multiple grounds from the guard lead |84. Test relay 110, upon energizing,

at 11| locks itself to grounded conductor 293, at

112 connects ground at armature 122 to conductor 364, at 113 starts the ringing machine, at back contact 116 causes the release of relay 100, and at front contact 116 grounds conductor 368 to operate connector group relay 422.

Busy relay 100 deenergizes when its circuit is opened by relay 110. At 102 relay 100 opens the busy-tone circuit, at 103 opens a point in the original circuit Vused on the reverting call, at 104 opens` a point -in the original energizing circuit vof reverting call relay 130 now locked in energized position, at 106 disconnects ground from the tone start lead, and at 109 prepares the circuit for ring relay 890. Connector group relay 422 energizes and at its upper contacts connects the link to conductors 61 and 58 of line 2|y to prepare the ringing circuit, Ringing relay 890 energizes when the pick-up conductor PU is vgrounded and connects No. 1 ring conductor to the positive line 58 as follows:l from ringing conductor by way oi 8l8, 885, 868, resistance R4, 866, 89|, 131, 182, 366, 3|6, to the lower contact of connector group relay 422, conductor 68 of v cable |59, and over the positive'fline conductor of line 2 'to the ringersconnected thereto. 'I'he proper code ring orthe proper generator is connected over this circuit to selectively ring sub-` scriber 2||. 1

When the called party answers, or in case the calling party should be the rst to answer, the ring-cut-ofl relay 180 is operated to disconnect the ringing circuit, and relays 150 and 6|3 are operated over Athe line loop as previously described. Relays-.608, 890, and 810 release, and relays 140 and 600 operate as previously described, except in this case when relay 140 operates the circuit to relay `12|) is opened at contact 14| to cause the release of relay 120. At 123 relay 120,. upon deenergizing, disconnects ground from conductor |88 to release relays 140, 420, 422, 3|0, and |22. At contact 125 relay 120 opens the circuit of time-cut-oi relay 608, at 124 removes the multiple ground from guard lead |84, at 122A relay 120 disconnects the multiple ground from link test lead 364 extending oy way of contact 112, and opens the locking circuit of ring-cut-off relay. 180 ywhich accordingly deenergizes. Atcontact 123 relay 120 disconnects ground from conductor |88 to cause the release of the nder relays |22 and 2|.0 and the connector relays 3| 0 and 420, and the release of relay 140. 'I'he finder and connector relays deenergize and open the lockin'g circuit of the reverting call relay 130. and the locking circuit of test relay 110 as well as the circuit o! the cut-oli relay of the calling and called line. Time-cut-off relay 608, upon deenergizing, at 606 removes ground ,from the guard lead |84, and at 601 grounds the al1-link busy conductor 669. All of the relays in the links are now in released position and the link may be used on other calls.

When the cut-off relay 60 deenergizes contacts 62 and 63 close the circuit for energizing the shunt-field line relay 10 over the line loop, at front contact 64 momentarily opens the circuit to lockout relay 50 and at back contact 64 grounds the permanent alarm conductor 99.

. Line relay 10 energizes over the subscribers loop,

at 12 grounds test conductor 56 to mark this line as busy in the connector end of the link,

` and at 13 maintains the locking circuit of lockout relay 50. The talking battery for both subscribers is taken through both windings of the line relay 10. When both subscribers replace their receivers after conversation then line relay 10 deenergizes to disconnect ground from conductor 56 to free the line at contact 12 and at 13 opens the circuit to lockout relay 50. Lock-- out relay 50vdeenergizes vto open the alarm circuit at 52, at 5| prepares a point in the circuit for marking the line as a calling line, and at 53 prepares a point in the start circuit. 

